In recent years, with the development of electronic information technology, the miniaturization and densification of electronic device installation and high volume and frequency of information, there is a higher demand for overall properties of the circuit base plate including heat resistance, water absorption, chemical resistance, mechanical properties, dimensional stability, and dielectric properties.
In term of dielectric properties, in a high frequency circuit, the relationship between signal transmission rate and the dielectric constant Dk of insulating material is: the lower the insulating material dielectric constant Dk, the faster the signal transmission rate. Therefore in order to get high signal transmission rate, the development of low dielectric constant base plates is required. With the increase of the signal frequency, the signal loss in the base plate cannot be ignored. The relationship between the signal loss and the frequency, the dielectric constant, Dk, and the dielectric loss factor, Df, is: the lower the base plate dielectric constant Dk and the dielectric loss factor Df, the lower the signal loss. Therefore the development of high frequency circuit base plate, which has a low dielectric constant Dk, a low dielectric loss factor Df and good heat resistance, becomes the common concern of the R&D direction of CCL factories.
There are lots of benzene rings in the polyphenylether resin molecular structure and there are not any strong polar groups. These properties give the polyphenylether resin its excellent properties such as high glass transition temperature, good dimensional stability, low coefficient of linear expansion, and low water absorption, especially excellent low dielectric constant and low dielectric loss. However, as a thermoplastic resin, the polyphenylether resin has some shortcomings, such as high resin melting temperature, poor processability, poor solvent resistance, etc. Due to the excellent physical properties, high heat resistance, chemical properties and electric properties of the polyphenylether resin, some big companies are interested in modifying the resin and some have achieved results. For example, the active groups have been introduced to the terminal or side chain of the polyphenylether molecule to make the polyphenylether resin into a thermosetting resin. After thermosetting, the resin has excellent overall properties such as heat resistance and dielectric properties, making it an ideal material for preparing high frequency circuit base plate.
In general, the way to use the modified polyphenylether resin comprising active groups in the terminal or side chains which can be cured, is to form a resin composition by coupling with a cross-linker. The cross-linker brings active groups that can react with modified polyphenylether. According to the literature, for the modified polyphenylether with C═C double bonds, the cross-linkers normally used include, e.g., polybutadiene, butadiene styrene copolymer, etc.
CN101370866A discloses the use of polyphenylether, butadiene, and bismaleimide resin composition in the preparation of a high frequency circuit base plate. Although the overall properties such as the dielectric of the plate are excellent, the butadiene reduces the heat resistance of the plate.
CN102161823 discloses the use of a resin composition copolymerized by a modified polyphenylether, a modified polybutadiene containing polar groups or a modified butadiene styrene copolymer containing polar groups with styrene in the preparation of a high frequency circuit base plate. Although the overall properties of the plate are excellent, the copolymer of polybutadiene or butadiene with styrene reduces the heat resistance and interlayer adhesion strength of the plate. Moreover, the polar groups on the molecular chain result in the increase of the water absorption rate and deterioration of the dielectric properties.